How do I know “how many joules” my weapon develops?

Home » How do I know “how many joules” my weapon develops?

Bullet speed, caliber and weight … no more!

How many times have we asked ourselves: how many “joules” will my weapon have?


To get a certain answer you do not need to be a Nuclear Astrophysicist (hat to them who know more than us!).

To me that I write, you who read… and theNuclear Astrophysicist that teaches… you absolutely need two data:

  • weight of bullet;
  • speed… obviously measured with a ballistic chronograph.

The mathematical formula?


The mass (weight) expressed in grains, multiplied by squared speed, expressed in feet per second, fraction the costant 450400… here is the result… expressed in feet per pound!!

Then you need to convert to joules…

It’s complicated?

With a calculator in hand I do not think so … yet there is a faster method.
Following is the script that Bill St. Clair gave us “strange people” who study weapons.


For decimal values use the “dot”, NOT the “comma”.

For this simple script we thank Bill St. Clair – Copyright © 2003 / 2017